Wafer level packaging (WLP) is the technology of packaging an integrated circuit (IC) at wafer level, and then single IC is singulated by wafer dicing. WLP is essentially a true chip scale package (CSP) since the resulting package is practically of the same size as the original semiconductor chip. WLP is capable of forming smaller packaging size with better electrical performance. Furthermore, WLP is a simple process, including chip packaging and test with a reduced overall production cost.
U.S. Pat. No. 6,107,164 discloses a wafer level packaging method, which is shown in FIGS. 1A-1D. As shown in FIG. 1A, a wafer 10 includes semiconductor chips at its front surface with an electrode metal pad 2 connected to electrode bump 4 via a copper interconnection or wire 3. Groove 22 is formed between two adjacent semiconductor chips by cutting the wafer 10 via a blade 21 to a depth deeper than half the thickness of the wafer 10. The front surface of the wafer 10 and the electrode bump 4 are covered with a layer of resin 23, as shown in FIG. 1B, with the resin 23 fully encapsulating the electrode bump 4. As shown in FIG. 1C, the resin 23 is then ground and polished by a polishing blade 24 until the electrode bump 4 is exposed from the resin 23. In this process, the top portion of the electrode bump 4 is also ground, therefore both the thickness of the resin 23 and the electrode bump 4 are reduced. As shown in FIG. 1D, the wafer 10 is then ground at its backside and the solder balls are attached on the exposed electrode bump 4. Individual packages are separated by cutting the wafer 10 from its back surface through the groove 22 using a blade 26.
However, during the process for grinding resin 23 and electrode bump 4 by the blade 24, metal dust from grinding the electrode bump 4 is easily to stick to blade 24, thus cause the grinding wheel to stop. As a result, the consistency of the exposed surface area of electrode bumps 4 is hard to control. In addition, some other problems are also generated, for example, the expensive molding compound and process time are wasted, additional processing cost is increased, and etc.